The PHILCO Phorum
Zenith Model K725 - Printable Version

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Pages: 1 2

Zenith Model K725 - Elijah - 01-16-2013

I'm trying to do an FM alignment on this one and the instructions say to adjust A12, A13 for maximum deflection. The top view in the Sams has arrows pointing to this IF for A12 and A13 at the top. I thought maybe A12 was on the top as there's only one hole for an alignment tool, and A13 must be on the bottom. There's nothing on the bottom. How can you align for A12 and A13 when there's only one screw at the top of this IF can?

[Image: http://i180.photobucket.com/albums/x220/ColColt/Misc%20Stuff/Old%20Radios/ScreenHunter_02Jan161837.jpg]

[Image: http://i180.photobucket.com/albums/x220/ColColt/Misc%20Stuff/Old%20Radios/ScreenHunter_01Jan161835.jpg]

RE: Zenith Model K725 - Glenn Roberts - 01-16-2013

the other is accessed through the bottom of the chassis.

Glenn

RE: Zenith Model K725 - Elijah - 01-16-2013

There's nothing there. There is no hole for your alignment tool. All I see is a screw with a nut holding the bracket of the can on.

This shows what I mean. You can see the bracket and no hole for alignment.

[Image: http://i180.photobucket.com/albums/x220/ColColt/Misc%20Stuff/Old%20Radios/ScreenHunter_03Jan161852.jpg]

RE: Zenith Model K725 - exray - 01-16-2013

I may be talking through my hat since I have no experience with this model but often the tool will reach beyond the first core on top to reach the second core.

RE: Zenith Model K725 - Elijah - 01-16-2013

That sounded feasible and I tried it but the next smaller tool I had that would just pass through the top adjustable core just went on past it to the bottom. I turned it side to side but no resistance as if I'd found that inner core.

Actually, I have the same situation on the AM band. They list adjusting A1, A2 the same way but no core on the bottom. The drawing actually says A1 Top and A2 Bottom or A11 Top and A10 Bottom but there is no bottom.?

[Image: http://i180.photobucket.com/albums/x220/ColColt/Misc%20Stuff/Old%20Radios/ScreenHunter_05Jan162024.jpg]

RE: Zenith Model K725 - Ron Ramirez - 01-17-2013

There are - or perhaps I should say were - alignment tools designed for these IF transformers that have the proper diameter hex tip, with a smaller diameter neck. This allows the tool to be used on upper and lower iron cores.

I used to have one of these tools, but since I try to avoid these "newer" radios, I never used it and have since lost it somewhere.

RE: Zenith Model K725 - Glenn Roberts - 01-17-2013

Quote:I used to have one of these tools, but since I try to avoid these "newer" radios.

Icon_biggrin Ron, I was waiting for "newfangled contraptions"

The M730 I did had the hole on the bottom, but I'm sure Ron is correct both slugs are on the top with a large hex or slot for one and a smaller hex inside for the second. Good Luck with it, they are nice radios but have a tendency to have the dreaded silver migration disease. Mine had it and had to rebuild all the coils, which was NO fun especially when you need a 2x power glass just to see the wire connectors inside the can.

Glenn

RE: Zenith Model K725 - Ron Ramirez - 01-17-2013

Actually, the hex holes in the slugs are the same size. The proper tool is narrow under the adjustment head to allow the lower core to be adjusted while not affecting the upper core's adjustment since the "neck" of the proper tool is smaller than the adjustment hole.

If I can find a picture of one later on, I'll post it...

Yup, consarn these doggone newfangled contraptions anyhoo... Icon_lol

RE: Zenith Model K725 - Elijah - 01-17-2013

Silver migration disease? I'm not familiar with that problem.

"I used to have one of these tools, but since I try to avoid these "newer" radios, I never used it and have since lost it somewhere. "

Ron, curry comb your house, your garage, the attic until you find it! Treasures await you if found.Icon_smile

RE: Zenith Model K725 - Glenn Roberts - 01-18-2013

This is for a philco but the problem is the same on brand "Z" sets.


http://www.philcoradio.com/phorum/printthread.php?tid=2807

Glenn

RE: Zenith Model K725 - Elijah - 01-18-2013

That was most educational. Those fellows knew what they were looking for and how to fix it. Some of the explanations were a bit confusing. I had never seen the inside of an IF can before. A little confused about the mica caps. They look like small pieces of plastic. Where would you get something like that to replace the bad ones? I suppose if you knew the values as in Nash's case, you could just wiring in a cap of the proper values across pin 2 and 3 of the IF.

As for the proper alignment tool, I ordered a set that includes the "Zenith alignment tool" hoping it will work.

http://www.tubesandmore.com/products/S-T8454

RE: Zenith Model K725 - Arran - 01-18-2013

If the radio is otherwise working I would recommend leaving the IF cans alone. I would also recommend looking for other sources of trouble before concluding that the IF cans are to blame as they are a bit tedious to open up and repair without good reason. The last problem that I had with an IF can wasn't silver migration it was a bad mechanical contact with the mica capacitors in the bottom which resulted in a volume drop any time the IF can got bumped.
Regards
Arran

RE: Zenith Model K725 - Elijah - 01-19-2013

It's working just out of alignment in that the stations/dial don't line up. Some stations I hear twice...just a quarter inch away from the other one.

I found out one thing today with this model. The chassis is tied to one side of the AC line. I won't be working on it again until I get that isolation transformer next week.

RE: Zenith Model K725 - Ron Ramirez - 01-20-2013

Finally, a picture of the tool you need...

[Image: http://i326.photobucket.com/albums/k420/mrphilco/Phorum%20Stuff/hextool.jpg]

Notice how the hex end is larger than the neck of the tool? This allows the tool to go down through the top slug to the bottom slug so that it may be adjusted without changing the adjustment of the top slug.

I took the picture from an eBay ad, with apologies to this seller who I hope won't mind if I link to his ad:
http://cgi.ebay.com/230915212377

RE: Zenith Model K725 - Elijah - 01-21-2013

If I'm not mistake that one is included in the set I bought that hopefully will be here soon.

http://www.tubesandmore.com/products/S-T8454